It is often necessary to couple the output of one or more optical fibers into one or more other optical fibers. This function is performed by switches or attenuators. The latter are designed to control, usually steplessly, the coupling efficiency. Many attenuator designs are already known; in some instances, a switch may be adapted to function as an attenuator and vice versa.
With the prevailing present trend toward miniaturization of optical transmission components, simple but reliable attenuating couplers that lend themselves to a size reduction are obviously at a premium. This cannot be said of many presently known proposals.
U.S. Pat. No. 5,226,104 to Unterleitner et al. describes an optical fiber coupler having an attenuating plate inserted between a fiber holder portion of the device and a reflecting mirror. The fixed mirror performs a coupling function only.
U.S. Pat. No. 5,208,880 to Riza et al. proposes a microdynamical fiber-optic switch which includes a piezoelectric actuator and a mirror coupled to the actuator. Governed by a controllable voltage source, the actuator displaces the mirror along a linear path such that an incident light is reflected from the mirror and deflected into a selected output connection port.
U.S. Pat. No. 5,185,675 to Banks describes an electro optic modulator for fiber optic transmission, the modulator having an elongated piezoelectric member which changes length when an electric field is imposed across it. A mirror is attached to a free-end of the piezoelectric member and strains or alternatively moves toward and away from a partially reflecting surface at the end of an adjacent optical fiber.
Other optical coupling systems are known e.g. from U.S. Pat. Nos. 5,133,030; 4,303,302; 4,950,884; and 4,924,870.
It is an object of the invention to provide a simple and reliable attenuating coupler for an optical transmission system, the coupler having a minimal number of components and thus amenable to miniaturization.
It is another object of the invention to provide a device as defined above having a minimal number of mechanical connections subject to wear with concomitant loss of accuracy.